This invention relates to an apparatus for measuring the surface geometries of objects by range finding based on triangulation. The invention relates particularly to a range finder which has the sensing part isolated from the controlling and analyzing part so that it can be used in extreme environments. More particularly, the invention relates to a range finder which operates on triangulation.
The prism 21 is fixed on a baseline length adjusting stage 41 which is in turn is mounted on a ball screw 44. If the ball screw 44 is turned with a motor 22 via a coupling 42, the prism 21 moves from side to side along a linear guide 46. The distance from the laser head 40 to the position of light projection from the prism 21 defines the baseline length, which is adjusted by linear movement of the prism 21. The motor 22 is controlled with a motor controller 23 fitted in the controlling and analyzing device 37 through a motor cable 34.
If this conventional range finder is used as a sensing eye on a robot arm (i.e., as a robot vision), it cannot analyze the surface geometries of objects (e.g. a surface geometry for identifying the positions of handling hook holes), making precise handling of the robot arm impossible.
The conventional surface geometry measuring apparatus comes in one of two major types: a device for measuring the distance to a point on the object spotwise is mounted on a device capable of two-dimensional movement 30 (e.g. an XY stage or an XY robot) and the point of measurement is moved two-dimensionally in a consecutive manner to profile the surface geometry of the object; or a device for measuring the surface geometry of the object (such as by a light section method) in a one-dimensional direction is mounted on a device (such as a linear stage or a direct-acting robot) capable of translation in the other one-dimensional direction and sectional shapes of the object are successively picked up to produce its overall surface geometry.
Whichever of these types of apparatus are used, it is necessary to use a mechanical element that permits the sensing part to be moved over the same range as the object and this increases the overall size of the apparatus. In addition, the sensing part uses semiconductor devices in both the light-projecting zone (e.g. a semiconductor laser or an LED) and the light-receiving zone (e.g. PSD or CCD) and, hence, is vulnerable to heat and radiation and difficult to use in extreme environments.
An object, therefore, of the present invention is to provide a range finder which is partly composed of components that are made of materials capable of withstanding use in extreme environments and which is otherwise composed of semiconductor devices.
Another object of the invention is to provide an apparatus that uses the above-mentioned range finder to measure the surface geometries of objects.
Yet another object of the invention is to provide an apparatus capable of measuring the surface geometries of objects in extreme environments such as high temperature and high radiation.
These objects of the invention can be attained by a surface geometry measuring apparatus which relies upon triangulation to measure the distance to an object from a sensor head comprising projection optics and observation optics, characterized in that said projection optics has a drive mechanism capable of adjusting the laser beam projecting position or the baseline length, said distance to the object is calculated by measuring the baseline length at the time when the point at which a spot of the laser light projected to said object forms a focused image on the observation plane in the observation optics has come to the center of said observation plane, said surface geometry measuring apparatus has a mechanism for causing said sensor head or observation optics to move or turn from side to side and a mechanism for causing said sensor head to turn up and down such that said moving or turning from side to side and said turning up and down allow the point of measurement on said object to be scanned with the laser beam two-dimensionally to measure the surface geometry of said object.
The projection optics which is one of the two components of the sensor head has a projection laser head and a prism or a mirror for changing the optical path of the laser beam, with the baseline length being defined by the distance from the laser head to the position of light projection from the prism or mirror. The baseline length is adjusted by linear movement of the prism or mirror on the sensor head. The observation optics which is the other component of the sensor head has a condenser lens and the laser beam projected from the laser head via the prism or mirror is reflected at the surface of the object to be incident on the condenser lens.
The sensor head in its entirety is moved from side to side by means of a motor and a direct-acting system; alternatively, the sensor head in its entirety or the observation optics which is part of it is caused to turn from side to side by means of a motor and a goniostage. On the other hand, the sensor head in its entirety is caused to turn up and down by means of a motor and a goniostage. As a result, the surface of the object is scanned with the laser beam two-dimensionally to measure its surface geometry. The projection optics and the observation optics are individually connected to the controlling and analyzing device via optical fibers.
The present invention also provides a baseline length variable range finder using triangulation to determine the distance from a sensor head in observation optics to an object, characterized in that a drive mechanism for adjusting the baseline length or the position from which projection optics projects light is provided and the baseline length for the case when the point at which a spot of the laser light projected from said position to the object forms a focused image on an observation plane has come to the center of the observation plane is determined to calculate the distance to the object.
In the range finder of the invention, the sensor head portion is solely composed of optical, mechanical and electrical parts that are made of quartz, SUS and other materials which will experience limited deterioration in extreme environments. The controlling and analyzing portion which must use semiconductor devices such as IC chips is isolated over distance from the sensor head so that it can be installed in ordinary and non-extreme environments.
In the range finder of the invention, the components of the sensor head and the cables and optical fibers for connecting them to the analyzing device are replaced with equivalents that have high resistance to extreme environments. The range finder of the present invention has the additional advantage of suppressing the errors of measurement and the increase in measurement times that would otherwise result from such replacement.